All passenger transport modes share one thing in common: they all need fuel to go places.
But how much fuel do they need?
And guess which one is the most energy-efficient?
Let’s take a look:

Source
According to UK data, coaches emit 0.023 kg of CO2 per passenger-kilometre; compared to 0.028 kg for trains, 0.14 kg emitted by cars and a minimum of 0.351 kg for airplanes, depending on the distance travelled.

Overall energy efficiency by passenger mode of land transport on a regional scale in France, in goe/p.km
Source: ADEME study on the energy and environmental efficiency of transport modes, 2008

Overall energy efficiency by passenger mode of transport on an interregional scale in France, in goe/p.km
Source: ADEME study on the energy and environmental efficiency of transport modes, 2008
Also, if you replaced subsidised air travel in the U.S. with inter-city buses, it would cut costs by 68% and CO2 emissions by 63,500 tonnes per year.
Hybrids are on the rise!

Similarly, hybrid technology helps reduce fuel consumption and reduces emissions by 20 to 30% according to French authorities.
Guadalajara is also expecting to reduce carbon emissions by 60%, by using hybrid buses compared to conventional diesel buses.
In London, every low carbon bus saves around 26 tonnes of CO2 compared with its diesel equivalent.
The world’s longest bus has an eco-hybrid engine and seats 256 people! A green move for the environment!